When the block to a successful repair is not a mechanical one

March 1, 2019
Man-made problems can take many forms. Sometimes a man-made issue is caused by an honest mistake. Other times it can be caused by a faulty part.

Man-made problems can take many forms. Sometimes a man-made issue is caused by an honest mistake. Other times it can be caused by a faulty part. In some circumstances the fault could be the result of a substandard repair that was made quite some time ago. Some may even argue that every issue with a vehicle is a man-made issue since man made the vehicle in the first place…I digress.  Regardless, stepping back for a moment and re-assessing the situation is in order. Each situation will be different. These issues can be broken down into a few different categories. Let us explore them individually.

Story #1: Insanity

We need to remember the cliché definition of insanity: repeating the same action over and over again and expecting a different result each time. An example of this would be: “I replaced the Mass Airflow sensor three times, so maybe the fourth MAF sensor will fix the problem.” I experienced this exact issue on a Mazda. A shop was on MAF sensor number four in an attempt to resolve a low power issue. The fault was actually a restricted catalytic converter. Maybe, in this case, they should have stepped back and reassessed the situation. What is the likelihood of getting four faulty parts in a row? I agree that faulty “new” parts could be an issue. Technically this was not a man-made issue initially, but needs to be recognized none the less.

Moral of the “Insanity” story: If a part does not fix the issue initially, step back and review your diagnostics. Accept the fact that you are human and you may have made an error. Learn from the mistakes and diagnose the next one more efficiently.

Story #2: Common sense

I was called to a shop to program a Jeep engine control module. I consulted with the shop prior to my visit and confirmed that a used JTEC (Jeep Truck Engine Controller) could be made to work on this particular vehicle. When I arrived, the technician informed me that they had replaced the valve body in the transmission due to a solenoid DTC. The vehicle started and drove into the shop before the repair and now the vehicle does not crank. The TCM (Transmission Control Module) no longer communicates with the scan tool but all other modules, including the JTEC, do continue to communicate. The technician “followed the charts” and determined that the JTEC needed to be replaced. Also, poking my head under the vehicle, I noted the transmission pan was not installed.

Does this scenario raise some questions? The vehicle cranked and started before the repair so what changed? The scan tool communicated with the TCM prior to the repair but now does not. What changed? The kicker: the TCM does not communicate but the JTEC does… so let’s replace the JTEC? I am not quite sure why the technician came to such a conclusion.

The diagnosis was actually quite easy. Maybe it was because I showed up with “a fresh set of eyes.” Maybe it was just common sense. My approach was to attack the “new” no crank issue. Connecting a scan tool confirmed that the TCM did not communicate. The JTEC did communicate and the gear selector PID indicated DRIVE. It is a pretty safe bet that this is why the JTEC is not commanding engine cranking. Since the valve body had just been replaced, I chose to disconnect the connector at the transmission valve body. Lo and behold, I regained communication with the TCM. The customer was informed that either the valve body had an electrical issue or improper installation had occurred. The valve body was replaced with another unit and the issue was resolved.

Here are a few common sense questions we should ask ourselves: Why would replacing a valve body cause a JTEC to fail? Why would replacing a JTEC solve a communication issue with a TCM? Why did the vehicle start and drive into the shop and now it does not start after a transmission repair? Most importantly, why did this technician go down the proverbial rabbit hole? We have all gone down this path at some point in our careers. In hindsight, I think we can all agree that the heat of the moment clouded our common sense. When confronted with “the hole” step back and gather your thoughts.

Moral of the “Common Sense” story: If things do not make sense STOP. Step back for a moment and reset your thought process to avoid the rabbit hole. If it seems like something does not make sense then it probably doesn’t.

Story #3: Do not be a slacker

Quality repairs do many things: fix the vehicle permanently, please the customer, please the boss, improve shop profitability and more. However, cutting corners on a repair might be sufficient (not acceptable) in the short term yet catastrophic in the long term. Piercing a wire for example could cause corrosion issues in the future. I constantly pierce wires for testing purposes but I always make sure to repair the wire I pierced with some acceptable type of sealant or wiring repair. My point: make a QUALITY repair to avoid future issues and come backs.

Figure 1 - Testing ground at pin 4 of the DLC resulted in bright test lamp illumination.

Here is an example of a sub-standard repair that caused the customer to spend lots of time and money when they should not have had to. In addition, a logical diagnostic process led to an accurate diagnosis in the end. The vehicle in question is a 2001 Dodge Ram 1500 with a 5.9 liter engine. The vehicle would crank and not start. Also, a “no bus” message was displayed in the odometer. The customer replaced the engine control module with a used unit and was requesting programming.

Figure 2 - Pin 5 of the DLC has a voltage drop that can be seen due to the lack of test lamp intensity.

Initial inspection confirmed that the MIL did illuminate and the vehicle was cranking and not starting. A scan tool was connected and communication was attempted. Ironically, the engine started when cranked. Disconnecting the scan tool caused the vehicle to stall. Reconnecting the scan tool allowed the vehicle to start again and disconnecting it yielded the same stalling result.

Figure 3 - A jumper wire was used to provide a good ground to pin 5 of the DLC.

Knowing that there is one power pin, located in cavity 16 of the DLC, and two ground pins, located in cavities 4 and 5, got me to thinking: could the scan tool be providing a missing ground between pins 4 and 5? A DLC breakout box was then connected in order to test the ground circuits. First, pin 4 was tested with a test lamp (Figure 1) and it illuminated brightly. Next, pin 5 was checked (Figure 2) and the same result was not achieved. The test lamp did illuminate but with much less intensity. The next step was to confirm our suspicion of the scan tool providing a ground for the vehicle. A jumper wire was installed between pins 4 and 5 (Figure 3). As suspected the truck started and ran. Disconnecting the jumper, no surprise, again resulted in a stalling situation. Time to trace some wiring diagrams.

Figure 4 - Touching the ground wire caused the substandard repair to fall apart.

Following the wiring diagrams backwards from the DLC leads to ground G105. This ground is shared by the DLC, PCM and many other components. Could this ground be the cause of all of our issues? Further research leads us to the ground location on the left front of the engine. It was obvious, when inspecting the ground, that a repair had been made. Touching the wire caused the replacement connector end and the ground wire to separate (Figure 4).

In this case, a shoddy wiring repair may have worked initially but failed further down the road. In Figure 5 it looks like the connector end that was chosen for the previous repair was too small for the copper wiring involved. Instead of choosing the appropriate connecter the small connector was “modified” to fit. I’m not sure, but it looks like no solder or crimping was used and the plastic heat shrink of the replacement connecter was relied on to hold the wire in place and maintain good electrical contact? This fault, and subsequent unnecessary PCM replacement, could have been easily avoided by performing a professional quality repair the first time around.

Figure 5 - This connecter was not even crimped or soldered together.

Moral of the “Don’t Be a Slacker” story: Do not cut corners on a repair. We are professionals so let us make sure our repairs reflect professional quality. Otherwise we risk inventing new problems later on down the road.

 Story #4: Not much you can do about it

The toughest man-made issues to diagnose are the odd ones that occur after a part is replaced and a new issue arises. Although this may sound similar to the valve body story from earlier in this article. The no crank issue from that story could have probably been easily found if the appropriate OE charts had been followed. What I am referring to now are issues where the OE charts would leave you hanging. Or even worse: “install a known good module and retest.”

These types of issues often require a creative way, using our knowledge and tools available, to design a test to prove what we want to know. For this example we will use a Durango… sorry it is another Chrysler product.

The subject vehicle is a 2002 Dodge Durango with a 4.7 liter engine. The vehicle was purchased at auction and, upon arrival at the shop, was determined to have a bad engine. A salvage yard engine was installed. The vehicle started and ran but, I was told, had mechanical issues. A second salvage yard engine was installed and now the vehicle cranks and does not start. The technician installed a spark tester and observed strong spark from the ignition coils. The engine did try to “fire” occasionally but never really started. It was probably a safe bet that fuel is getting to the engine due to the occasional firing, but to be sure the technician installed a fuel pressure gage and the results were within specification. As a last ditch effort the technician used starting fluid to no avail. At this point I got the call.

My first step was to plug in a scan tool. Of course, the auction vehicle had a dead battery and, as a result, no DTC’s were stored. A charged battery was installed and testing resumed. Cranking the engine did show engine RPM on the data list and no other data PID’s appeared to be out of whack. Given the situation I had a few questions: What was the mechanical condition of the used engine? We had some spark, but was it occurring at the appropriate time?

Figure 6 - A relative compression test shows 2 ignition firing events and then about 8 crankshaft revolutions before firing again.

The next step was to perform a relative compression test to determine if the engine had equal compression across all cylinders and to get a rough idea of spark timing. A scope capture was obtained (Figure 6) and something definitely did not look right.

If each current peak in the capture resembles a compression stroke, then why are there around 30 compression events on this 8-cylinder engine between firing events? The engine appears to have some mechanical integrity so ignition timing will be investigated next. Ignition timing, on most modern vehicles, is based off of the crankshaft position sensor signal. The decision is made to scope the crankshaft and camshaft sensors and move forward from there.

Consulting wiring diagrams in service information revealed that this vehicle had two possible engine control diagrams. One is for a 4.7 liter engine equipped with a JTEC engine controller and the other is for a 4.7 liter engine with an NGC (Next Generation Controller.) The two options were easy to distinguish from one another because a JTEC has three connectors while an NGC sports four connectors. This Durango was equipped with a JTEC and the appropriate scope connections were made. A scope capture (Figure 7) was obtained and compared to a known good capture.

Figure 7 - The capture obtained from the Durango is for an NGC controller not for the JTEC with which it is equipped.

The scope capture that was obtained looked great if the Durango had an NGC. However, this vehicle’s JTEC is expecting a completely different pulse train from both the CKP and CMP. Both the crankshaft and camshaft reluctors were wrong for the vehicle.

This vehicle had the wrong engine installed and needed to be replaced for a third time to resolve the issue. This can be a problem when salvage yard parts are used and is more common than one might think.

Story #5: Not much you can do about it – Part II

This last vehicle was a Mazda 3 that had a used engine installed just like the previous Durango example. Only because it is important for the diagnosis, I would like to point out that this vehicle was in the Chicago Illinois area. The Mazda ran and drove fine after the engine was replaced with the exception of MIL illumination for a P0171 Lean Exhaust Bank 1 DTC.

This vehicle landed in the bay of a second shop when the first shop threw up their hands. The shop consulted with me on the phone and relayed fuel trim data to me. The fuel trim numbers were equally positive under all conditions which suggests that the existence of too much Ethanol in the tank of this non-flex fuel vehicle was a strong possibility. An Ethanol test was performed and the fuel was well under the ten percent mark.

When I visited the shop, and connected the Mazda IDS, I noticed on the vehicle ID screen that the vehicle conformed to California emissions requirements. What do you think the chance of finding a California emissions engine in a Chicago area salvage yard is? Further research confirmed that the fuel injectors for a California emissions application had a higher flow rate than the non-California counterpart. If the injectors now have a lower flow rate than the injectors the PCM thinks it is driving the engine will indeed run lean. A set of California fuel injectors was ordered, installed and the fuel trim numbers came right back in line.

Moral of the “Not Much You Can Do About It” stories: Salvage yard parts are not always a bad choice, but occasionally an unforeseen issue can blindside you. When this happens, a creative approach to diagnostics, observation of even the smallest details and additional research will help one find the resolution to the issue.

In summary, man-made issues are unavoidable. Weather it is your fault or not, the vehicle still needs to be fixed. Professional repair techniques will help avoid some of these issues. Common sense diagnostics will help avoid some of the rabbit holes. And observation, research and creative thinking should help resolve the rest.

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